1. Field of the Invention
The present invention relates to a high power light source, in particular to a light source comprising a plurality of high power laser diode modules arranged in high density.
2. Related Art
In general, a laser diode module is used as a signal light source for an optical fiber communication, particularly a trunk line system—CATV or an excitation light source for a fiber amplifier. In order to achieve a high power and a stable operation, the laser diode module includes a built-in Peltier device, and in addition, optical parts such as a laser diode chip, a photodiode chip, lens or the like as well as electric parts such as a thermistor component, inductor, resistor or the like are arranged on a metal substrate mounted on the upper part of the Peltier device.
The above-mentioned Peltier device comprises a thermoelectric semiconductor. More specifically, when a DC current is supplied thereto, heat is transferred in the current flow direction, in case of p-type semiconductor, and heat is transferred in the direction opposite to the current flow, in case of n-type semiconductor, thus a temperature difference occurs at both ends of the thermoelectric semiconductor. The cooling system employing the Peltier device implements cooling (i.e., heat absorption) at the low temperature side thereof and heat dissipation at the high temperature side thereof, taking advantages of the property of the above-mentioned temperature difference.
The laser diode module detects the temperature of the chip by means of a thermistor element adhered to the vicinity of the above-mentioned laser diode chip. The laser diode module has a structure in which the Peltier device is driven through the feedback of thus detected temperature value to cool the whole metal substrate where the laser diode chip is arranged, thus keeping the temperature of the laser diode chip constant.
Japanese Patent Provisional Publication No. 10-200205 discloses a semiconductor laser module provided with a metal substrate comprising two kinds of metallic material.
However, in recent years, a higher cooling capacity and a higher temperature-environmental reliability (i.e., ability to sustain a normal function even when the temperature varies) of the laser diode module are demanded more and more strongly according to the realization of the higher power in the laser diode module.